1. Field of the Invention
The present invention generally relates to a fine zirconium oxide powder and a method for producing the same. More specifically, the invention relates to a fine zirconium oxide powder used as an additive to electronic parts, and a method for producing the same.
2. Description of the Prior Art
In conventional electronic parts such as capacitors, zirconium is used as an element for shifting the Curie point. Zirconium is added mainly as zirconium oxide when raw materials are mixed with each other, and then, sintered by a solid phase reaction in a sintering process. A fine zirconium oxide powder used for such a purpose is obtained by calcining a hydrated zirconium, which is obtained by a hydrolysis or neutralization reaction from an aqueous zirconium solution, after or without drying the hydrated zirconium, and thereafter, by causing the calcined powder to be dispersed in water serving as a solvent to be dried and ground.
For example, there is known a method comprising the steps of: mixing a zirconium powder material having a mean particle size of 0.8 μm or more in a solvent of one or more kinds selected from the group consisting of water, alcohols, aromatic hydrocarbons, esters and Cellosolves (trade name, commercially available from Union Carbide Corp.), to prepare a slurry; adding an organic acid, a polyelectrolyte, a surface active agent or the like to the slurry as a dispersing agent; and grinding the slurry by means of a grinder (see Japanese Patent Laid-Open No. 11-35323). Furthermore, at the dispersing step, there are some cases where a solvent other than water is used in order to enhance dispersibility, and alcohols, ketones and aromatic hydrocarbons are often used.
However, if the solvent and dispersing agent disclosed in Japanese Patent Laid-Open No. 11-35323 are used, the particle size distribution is widened during dispersion. If such a fine zirconium oxide powder having a large particle size and a wide particle size distribution is used as the additive, there is a problem in that the starting temperature in the sintering reaction of a reactant, to which the fine zirconium oxide powder is added, is raised.